The present invention is directed to implantable devices for stabilizing the spine. Specifically, the invention concerns intervertebral spacers expandable from a reduced size insertion configuration to an expanded size spacing configuration.
Intervertebral discs, located between the end plates of adjacent vertebrae, stabilize the spine, distribute forces between vertebrae and cushion vertebral bodies. An intervertebral disc may deteriorate due to trauma, aging or disease resulting in pain or discomfort to a patient. One common procedure for relief of patient discomfort is a discectomy, or surgical removal of a portion or all of an intervertebral disc. Often, this is followed by implantation of a device between adjacent vertebrae to maintain or restore disc space height. Typically, implantation of such a device is also intended to promote bony fusion between the adjacent vertebral bodies.
One limitation on the size of a device inserted into the disc space is the size of the opening through surrounding tissue that is available to gain access to the disc space. From a posterior approach to the spine, the dura and nerve roots must be mobilized to gain access to the disc space. Similarly, from an anterior approach, the aorta and vena cava must be mobilized to gain access to the disc space. Such mobilization is often limited by the anatomical structures, thus resulting in a relatively small access site. Removal of additional bone to enlarge an entrance to the disc space may weaken the joint between two adjacent vertebra. Moreover, excessive retraction of vessels and neural structures to create a large access opening may damage these tissues. Thus, prior procedures have been limited to placing a first device passable through the available opening on one side of the spine and mobilizing the tissue or vessels to place another similar implant on the opposite side of the spine. Each implant being limited in size by the available access site.
Thus, there remains a need for implantable devices that have a reduced size insertion form and are expandable in the disc space to a larger size for enhancing spine stability and facilitating immobilization via bony fusion.